Various processes to make cyclic alkylene ureas have been described in the literature and in patents, such as in J. Org. Chem. 1950, vol. 15, pages 471 to 474, and 475 to 480, relating to the synthesis of ethylene urea from urea and ethylenediamine, and from ethylene glycol or ethanolamine and urea, or carbon dioxide and ammonia.
As early as 1886, E. Fischer and H. Koch reported in Annalen, vol. 232, page 227 (1886), the preparation of ethylene urea by heating ethylenediamine and diethyl carbonate at 180° C. As described therein, this reaction was carried out in a sealed tube and required the use of high temperature.
In Shenoy, P. K. et al., American Dyestuff Reporter, May 6, 1968, pp. 17 to 34 (352-369), a variety of processes is disclosed for the preparation of ethylene urea (2-imidazolidinone) and derivatives of ethylene urea. At page 18 (353), it is stated that aminoethylethanolamine and urea can be reacted at a temperature of from 100° C. to 180° C. to give N-(2-hydroxyethyl)ethyleneurea. Also, at page 18 (353), it is stated that N-(2-hydroxyethyl)ethyleneurea can be prepared from the reaction of aminoethylethanolamine and diethyl carbonate. At page 19 (354), it is stated that N,N′-(dimethyl)ethyleneurea can be prepared by reacting ethylene urea with formaldehyde followed by catalytic hydrogenation with a nickel catalyst, or by using formaldehyde-formic acid reduction of ethylene urea.